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A051592 Numbers n such that n!!!!!!-1 is prime. 3
3, 4, 6, 12, 14, 54, 74, 102, 114, 302, 318, 366, 614, 1178, 1188, 3110, 7284, 21432, 21906, 25848, 29882, 38618, 41990, 84510, 86022 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

n!!!!!! = n(n-6)(n-12)(n-18)...

The search for multifactorial primes started by Ray Ballinger is now continued by a team of volunteers on the website of Ken Davis (see link).

LINKS

Table of n, a(n) for n=1..25.

Ray Ballinger, Status of Search for Multifactorial Primes

Ken Davis, Status of Search for Multifactorial Primes

Ken Davis, Results for n!6-1.

MATHEMATICA

MultiFactorial[n_, k_] := If[n < 1, 1, n*MultiFactorial[n - k, k]];

Select[Range[0, 1000], PrimeQ[MultiFactorial[#, 6] - 1] & ] (* Robert Price, Apr 19 2019 *)

CROSSREFS

Cf. A085158 (sextuple factorials), A085150.

Sequence in context: A294144 A136243 A250985 * A044843 A293593 A024373

Adjacent sequences:  A051589 A051590 A051591 * A051593 A051594 A051595

KEYWORD

hard,nonn

AUTHOR

N. J. A. Sloane

EXTENSIONS

Edited and extended by Hugo Pfoertner, Jun 23 2003

Corrected and extended by Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 03 2008

STATUS

approved

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Last modified May 26 02:56 EDT 2020. Contains 334613 sequences. (Running on oeis4.)